Telephone system



W. SETZEPFAND TELEPHONE SYSTEM May 3. 1927. 1,627,206-

F1ed`June 26, 1926 Patented May 3, 1927.

UNITED sTATEs vPATENT oFFIcE.

WERNER SETZEPFAND, F BERLIN, GERMANY, ASSIGNOR T0 SIEMENS & HALSKE AKTIENGESELLSCHAFT, 0F SIEMENSSTADT, NEAR BERLIN, GERMANY.

TELEPHONE SYSTEM.

Application led June 26, 1926, Serial No. 118,646, and in Germany July 6, 1925.

My invention relates in general to methods of constructing repeating coils, and more in particular to methods of constructing repeating coils which Ahave a high degree of symmetry and balance.

In telephony, repeaters are used for making phantom circuits and they form tappinfY coils. For this purpose, repeaters are neede .having theinwindings completely symmetrical to the tapping oint, otherwise crosstalk would occur. T is symmetry must be present for the absolute values and for the variations. In the ordinary repeaters it 1s comparatively easy to make the absolute l5 values symmetrical. But theI capacities of the different coils cause phase variations, which render the s mmetrical values of the repeaters worse. arious methods of winding are known, which enable the capacities of the coils to be made equal. But all of them require special cpreliminary work to be done on the pre are wire or special measures to be taken uring their construction which render the operation of winding delicate and expensive. If thereafter faults of any kind are found while testing, the work that has been performed for increasing the symmetry of the values is lost.

These disadvantages are avoided by the balancing process, to which the invention re-l lates;` because it permits every ordinary tapping coil to be completely and symmetrically alanced without affecting its construction and its other electrical values, this being effected-by adding suitable capacities to the lcircuit in order to adjust the difference in phase. The balancing takes lace at the iinlshed repeater, hence it nee only be done at those tapping coils, that are used for ob-` taining the phantom circuit. Equalization is accomplished by adding one or more .fixed condensers, which are preferably built into the casing.

The location and value of the condenser or condensers are determined by suitable electrical tests of the coils o the repeater. These tests are of such a character as to determine not only if a difference of phase exists, but also the degree of unbalance. Condcnscrs of the pro r values, approximately, are then connect around those coils where they are required. A

The drawing. shows, by way of example` a circuit, whic has the phantom formed by means of repeaters that are made symmetrical according to the invention. The. repeaters U1 and U2 are inserted in the physical leads a1, b1 and a2, ZF. U3 is the repeater for forming a phantom circuit from two pairs-of physical leads a1, b1 and a2, b2. The symmetrical equalization according to the invention is obtained by means of the condensers C1, C2 and C1', C2. t What I claimis:

The process of constructing a repeating coil having two windings which are each symmetrical to a center tap, which consists in cqualizing the windings during construction so far as the absolute values of'resistance and inductance are concerned, but with outspccial regard'to phase differences due to capacity unbalance, in testing the finished rcpcatmg coil to determine if any capacity unbalance exists and the amount of such unbalance, and in adding condensers of the proper value and inshunt of the coils which lrequire them, as indicated by the' test, so l as to make the finished repeater completely symmetrical.y i

In witness whereof, I hereunto subscribe my name this 2nd day of June, A. D. 1926. .i

WERNER'SETZEPFAND. i 

